The U.S. drafted Parameters for a Joint Comprehensive Plan of Action (JCPOA) between the EU/E3+3 negotiators and Iran is a remarkable achievement. It has excellent specificity on technical constraints, timelines, and sequencing. The terms spell out a fair and equitable deal for all parties. JCPOA will allow Iran's peaceful nuclear program to grow at a natural pace, is effectively verifiable, and provides a solid fifteen year window during which the United States and other members of the P5+1 can build stronger relationships with Iran to reduce Iran's incentives for nuclear weapons. The negotiators are to be congratulated!

There are, however, important outstanding elements that must be clarified in the coming months. The text of the JCPOA says that no uranium enrichment will occur at Fordow, and that approximately two-thirds of the current 2976 centrifuges installed there will be removed. This leaves about 1000 centrifuges at Fordow, with some fraction enriching elements other than uranium. Although the Fordow capability is notionally a non-uranium capability, unless specifically designed to be incompatible, those centrifuges could be rapidly repurposed for enriching uranium under a breakout scenario. If those centrifuges are only first generation IR-1 centrifuges, they will not significantly affect the breakout calculation. U.S. officials have confirmed that this is their understanding, however, the text of the terms released leaves some ambiguity.

Other oustanding questions do not enter the breakout calculation, but are nonetheless important and will take considerable effort. For example, the extent of research allowed could be more carefully sepecified: will research on laser enrichment or other isotope separation and isotope breeding techniques be allowed at sites other than Fordow? Also, the mechanism by which Iran will maintain its LEU inventory below 300kg UF6 needs to be specified. The parameters for the redesign of the Arak reactor are already well in hand, but arrangements for exporting spent fuel will be difficult to negotiate. Principles for the long-term enrichment plan beyond 15 years needs to be resolved.

Many of these outanding areas are also issues for other emerging nuclear-power countries. The excellent work of the negotiating teams lays the ground not only for a peaceful resolution of the Iran nuclear issue, but can also help address the connection between nuclear power and nuclear proliferation more generally. If it takes up the charge, Iran can become a leader in securing a world free of nuclear weapons, helping to find ways for others to share in the fruits of nuclear energy.